What do you do if you didn't buy a big enough present??

I was torn between wanting to get something nice for my friend's DD for her 2nd birthday and also not wanting to set a precedence plus we are having to tighten our purse strings significantly. The gift was bought when her DD wasn't going to have a party, so I was just going to pop it through the letterbox on the day and not make a big thing about it. My friend then decided a week or so before the big day that she would have a tiny party and my DD plus one other was invited. I didnt' think any more about it and off we trotted. DD had a fabulous time but our pressie was noticeably small . Should I just leave it?

Thank you everyone for your reassuring replies - it's just very cringey isn't it?? Oh the minefield.....! My friend of course doesn't know any of the background as to how the gift came to be and I really don't want to explain it, so I will just leave it and hope that all is well. The trouble is that she's a good friend but she was going to have a joint party for her DD with all her NCT crowd (and not us) and I think she felt awkward about that so I didn't want to exacerbate that when the original choice was made.